[vsnet-grb-info 23598] ZTF19abvizsw: No counterpart candidates from Swift/BAT targeted search

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25697
SUBJECT: ZTF19abvizsw: No counterpart candidates from Swift/BAT targeted search
DATE:    19/09/10 03:31:59 GMT
FROM:    Aaron Tohuvavohu at PSU/Swift  <auc444 at psu.edu>

Aaron Tohuvavohu (U Toronto) reports:

We have performed a search for an un-triggered GRB counterpart to the
claimed afterglow candidate ZTF19abvizsw (GCN 25616, 25643, 25658) in
the Swift/BAT raw light curves. The temporal window for the search was
chosen to be 2019-09-01 07:35 --- 2019-09-02 03:08 corresponding to
the times of the last ZTF non-detection and of the discovery
observation respectively.

During this time period, the location of ZTF19abvizsw was above the
Earth-limb with respect to the spacecraft (and thus a priori capable
of depositing flux onto the detector) 64.2% of the time. The location
was inside the BAT coded field-of-view 19% of the time.

No compelling candidates were found in the BAT raw light curves with
time bins of 64ms, 1 s and 1.6 s. Due to the long temporal window for
the search, the average background, and thus upper-limit sensitivity,
varies widely over the search window. After excising times when the
spacecraft was near the South Atlantic Anomaly, the average 5-sigma
flux upper limit achieved for a long GRB in the 1-s binned data with a
typical spectrum corresponds to ~3 x 10^-7 erg/s/cm^2 in the BAT coded
field-of-view, and approximately an order of magnitude higher for
locations outside of the field-of-view.

We also performed spot checks for the three candidates reported from
INTEGRAL (GCN 25686). None of these candidates are seen in the
Swift/BAT data.